Identify the muscle that adducts the scapula and aids in extension of the head.

Correct Answer: D

Rationale: Trapezius adducts the scapula, pulling it toward the spine, and extends the head backward when both sides contract. Buccinator compresses cheeks. Serratus anterior protracts scapula, not adducts. Sternocleidomastoid turns the head. Trapezius' dual role in scapular and neck movement sets it apart, key for posture and head positioning.

Correct Answer: A

Rationale: Myasthenia gravis, an autoimmune condition, weakens muscles by antibodies destroying acetylcholine receptors, impairing nerve-muscle signals, causing fatigue. Amyotrophic lateral sclerosis (ALS, Lou Gehrig's) is neurodegenerative, not autoimmune. Fibromyalgia is pain-focused, not receptor-based. Myasthenia's receptor-specific weakness sets it apart, treatable with immunosuppressants, distinct from nerve or pain conditions.

Correct Answer: A

Rationale: The coronal suture runs transversely across the skull, separating the frontal bone (forehead) from the two parietal bones (top sides). This suture, visible as a line in coronal section, allows cranial growth in infancy and fuses later. The sagittal suture, midline, joins the parietal bones, not the frontal. The lambdoid suture separates parietals from the occipital bone posteriorly. 'Frontal' as a suture is incorrect it's the bone itself. The coronal suture's position and function distinguish it, essential for skull structure and development, unlike sagittal or lambdoid orientations or misnamed bone references.

Correct Answer: D

Rationale: Adipose tissue is the body's largest endogenous substrate source, storing vast triglyceride reserves thousands of grams far exceeding other stores, providing energy via lipolysis during prolonged activity. Muscle glycogen, about 300-500 grams in trained individuals, fuels local contraction but is limited. Liver glycogen, around 100 grams, maintains blood glucose but depletes quickly. Intramuscular lipids, small triglyceride droplets, contribute modestly, far less than adipose's capacity. Adipose tissue's sheer volume and energy density (9 kcal/g) dwarf glycogen's stores (4 kcal/g), distinguishing it as the primary reserve, key for sustained energy needs beyond glycogen's scope.

Correct Answer: C

Rationale: Pectoralis major has a convergent fascicle pattern, with fibers fanning from a broad origin (clavicle, sternum) to a narrow insertion (humerus), enhancing force for arm adduction and rotation. Biceps brachii has parallel fascicles along its length for elbow flexion. Gluteus maximus features multipennate fibers for hip extension. Rectus femoris runs parallel for knee extension. Convergent patterns concentrate force from multiple directions, distinguishing pectoralis major's structure and function, key for chest movements, unlike parallel or pennate arrangements.